carbon in cabin filters

Joined
Apr 18, 2009
Messages
169
Location
Alabama
How long does the carbon in cabin filters last? Nowhere have I seen this addressed. I'm aware it may be beneficial to air quality while filtering but does it also cut down on efficiency? At what point does it stop working?
I ask because my suspicion is that it boils down to a marketing ploy.
 
That's a really good question and something not likely to be answerable in reality. Why? Because the sorbents have a specific capacity, and they follow what's called an adsorption isotherm; effectively, the capacity is lower at lower concentrations and higher at higher concentrations. On top of that, there's natural diffusion.

So if you live in a polluted area, the filter may be scavenging diffusing pollutants even when the system is off and car parked, affecting capacity. But if you drive through a more polluted area, it may still pull some more out because of the isotherm.

On top of that, some are really big/long, and some are pretty small. So the mass of adsorbent is variable.

Id argue that it is more marketing ploy in the end. That said, the use of activated carbon to remove organics is legitimate, and so to some extent, until the sensitivity of your nose states otherwise, this is a "comfort" capability that gets swapped at the recommended interval (12mo/12k???) or if you start noticing something different...

Its not a tough calculation to assume some airflow, some ppm of pollutants, some capacity per gram of carbon, and how much carbon is needed... and then notionally add that amount in the filter. I dont know the basis of calculation, so couldnt say if the true amount is grams or kilograms...
 
I'd just at least check it yearly usually twice a year in case Mighty Mouse got in there. He will either set up shop on top sand make a mess or sail through it like a hot knife through butter. The he will do his thing in the heater ducts. Then you'll notice you are picking hay, insulation or bird seed out of your teeth rather often and it STINKS🙊.
 
My 4-series has a two-year change interval and the Genuine filter is carbon impregnated.

(I was going to share a photo of the filter I just changed but because of the carbon you can't really tell how dirty it was other than the collection of odd number of crushed leaf material)
 
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I use activated carbon filters in my own vehicles. They cut dramatically down on external odors making it into the cabin. These filters remove odors, chemicals, gases and VOCs. I really noticed a huge difference between outside and inside air during the last few fire seasons. I notice it when I drive past the local sewer treatment plant or whenever I drive behind a diesel-powered vehicle and at every gas station. I usually replace the cabin air filter once a year, in case of heavy load due to fires and other fine particulates twice a year.
 
For allergies and asthma you should use a HEPA cabin air filter. Bosch makes them. They are better at filtering pollen, mold and dust. Carbon filters remove primarily gases, fumes, and odors but they are not great for removing fine particulates.
 
Originally Posted by vavavroom
For allergies and asthma you should use a HEPA cabin air filter. Bosch makes them. They are better at filtering pollen, mold and dust. Carbon filters remove primarily gases, fumes, and odors but they are not great for removing fine particulates.


Tried them and they did no good period for my wife!
 
Sorry to hear that. Maybe some irritant is inside the vehicle. Brominated flame retardants, pvc, chlorine, and plasticizers can all cause allergic reactions or trigger asthma. My mom had to get rid of all the carpeting in her car because it made her wheeze.
 
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